1. Field of the Invention
The invention relates to a fiber-optic sensor for liquid-immersion detection configured to detect the dry/wet state of the environment which the sensor is in, for example.
2. Description of Related Art
Recently, the capacity of data transmission has increased rapidly with the flourishing development in the internet, where pictures and images of high quality occupy a large portion of the bandwidth. As a consequence, the usage rate of optical fibers increases significantly. Triple-play service including voice, data and image provided through optical fiber network has gradually become the mainstream method for transmission.
Since optical fiber network has extended to a wide range, the water immersion occurring on the optical fiber communication wiring or the cable wiring at joint box, roadside cabinets, or portion at underground duct needs to be detected in real time for technicians to eliminate the water immersion.
A typical commercial product includes a liquid level sensor which is mainly disposed in a sensor of a single location. The surface of the sensor is easily affected by external environmental factors (i.e. dust), and the function of the sensor is thus influenced thereby, which makes the sensor not fit to be disposed on the optical fiber detection wiring. Although other sensors have been proposed for detecting the water immersion of the optical fiber wiring, the sensing mechanism here is to use a non-woven cloth to absorb water, where the non-woven cloth swells so that the optical fiber results in bending loss, and to observe with an optical time domain reflectometer (OTDR). Nevertheless, the bending loss of this sensor is as high as 10 dB when immersed by water, such that the water immersions occurring at multiple locations can not be observed on the OTDR at the same time. Moreover, the subsequent detection wiring may easily break down due to the breakage of one of the detection points.
Therefore, researches have been carried out for efficient detection of the water immersions on optical fiber network.